Multitube reactors are ubiquitous in the manufacture of commodity chemicals. These reactors, which may comprise a normally substantially vertical vessel further comprising a plurality of open ended reactor tubes, are typically used for catalyzed gas-phase reactions. The shell of a multitube reactor for such processes may typically have a diameter of several meters and include from as few as about 5000 up to as many as about 50000 reaction tubes. Each reactor tube may be as long as 5, 10 or even 15 meters.
In such reactors, the upper ends of the reactor tubes may generally be affixed to an upper tube sheet and be in fluid communication with a fluid inlet head above the upper tube sheet. Similarly, the lower ends of the reactor tubes may generally be affixed to a lower tube sheet and in fluid communication with an effluent collecting head below the lower tube sheet. During normal operation, the desired reactant gases are supplied to the fluid inlet chamber at the upper ends of the reactor tubes and passed therethrough. Effluents leaving the lower ends of the reactor tubes are collected in the effluent collecting head. The heat of reaction is removed by a heat transfer fluid which is passed across the outer surfaces of the reactor tubes.
Due at least in part to the multiplicity of reactor tubes utilized, temperature control in multitube reactors can be challenging, Yet, precise temperature control may often be desirable, or even required, within many manufacturing processes. For example, accurate temperature control can be critical in maintaining the desired reaction rate. Process inhomogeneities, e.g., hot spots, if allowed to occur, can result in increased reaction rate and conversion, which for many reactions; can result in an undesirable decrease in selectivity. And, undesirable temperature fluctuations can detrimentally impact any thermally sensitive components or inputs utilized in the reaction. For example, undesirably fluctuating temperatures can lead to reduced catalyst life, and degradation of thermally sensitive components, which, in turn, can result in fouling of the reactor tubes.
When considering the challenge of appropriate temperature control within a multitube reactor and a process comprising the same, the residence time of reaction components within the process, and more particularly, at a particular temperature within the process, must also be considered. That is, the detrimental impact of ineffective temperature control may be exacerbated if reaction components have a residence time at the suboptimal temperature that allows for an increase in conversion and/or reaction or decomposition of thermally sensitive components.
It would thus be desirable to provide an improved multitube reactor, wherein such considerations have been taken into account, and the aforementioned challenges have been substantially overcome.